The present invention relates to tamarind seed gum and, more particularly, to a method for upgrading the crude seed gum.
Tamarind seed gum, with a polysaccharide content of 45-55%, has long been recognized as a potential industrial polysaccharide source. Tamarind gum may be used as an inexpensive textile size, a paper strengthening agent, as well as, a substitute for other gums in various uses. Wide application of the seed gum, more specifically, tamarind seed kernel powder, (hereinafter TSKP), has been limited to date, however, because of the presence of the non-polysaccharide portion. The following is the typical composition of crude TSKP.
______________________________________ Non-Polysaccharide Components . . . . about 45-55% Protein 17-19% Moisture 8-10 Fat 7-8 Fiber 3-5 Ash 2-4 Tannin 2-3 Free Sugars 2-3 Mechanical Impurities.sup.(1) 0-5 ______________________________________ .sup.(1) The term "Mechanical Impurities" as used herein, will mean such materials as sand, dirt, seed hulls, stems and the like. Polysaccharide (by difference) .... about 55-45%. In some instances the polysaccharide content may be somewhat higher such as 65% and above, particularly if the moisture and/or fat content is reduced.
Presence of the large non-polysaccharide fraction -- chiefly protein, fat and fiber -- is undesirable because it contributes little or nothing to intended applications and it can interfere with or complicate product handling and use. For example, fat in TSKP makes the product tacky and non-free flowing. As a result, such TSKP is difficult to convey and difficult to disperse. Protein in TSKP may produce foam during dispersion in aqueous systems and is prone to solution denaturation with resultant formation and precipitation of insolubles. These materials, as well as, the water-insoluble fiber in TSKP can build up in the processing equipment and necessitate periodic shut-down for removal.
A number of purification processes have been devised to upgrade the crude gum and reduce the various use disadvantages. In general, these processes fall into two classifications: aqueous and non-aqueous processes.
Aqueous processes attempt to selectively remove polysaccharide or protein from the crude TSKP. Such processes have not been completely satisfactory because no totally selective extractant has been found for either tamarind polysaccharide or tamarind protein. Further complicating these processes is the fact that selective removal of protein, even if complete, would leave fat, fiber and other non-polysaccharide residue in TSKP. Also, tamarind polysaccharide significantly thickens aqueous extracts. Thus, polysaccharide extraction processes must be conducted at low TSKP concentrations (typically, about one percent) to permit physical separation of fractions. Recovery of product, such as by alcohol precipitation or by drying, is difficult and expensive because of the large volumes that must be processed.
Non-aqueous processes attempt to take advantage of differing TSKP component densities in order to separate the components in organic solvents. Here also, separation is not complete nor selective. A further disadvantage of these processes is that the use of flammable solvents is necessary. These solvents represent a potential health and safety hazard and necessitate the use of costly explosion-proof equipment in explosion-proof areas.